Wayward Handling When Braking At Speed

[Dom]

Afternoon, All.

I'm experiencing the above, despite recently upgrading to HiSpecs on the front. What should I check? Shocks? Bushes? Anti-roll bar?

How positive should the brakes now feel? The initial bite is not as good as I had hoped for. Overall, the upgrade has been an expensive disappointment. I still don't feel confident the car will pull up quickly and in a straight line, especially when driven as a sports car. Put it this way: the brakes on my Defender feel more positive!

[theelanman]

How are you brake proportion valves.......
The ones front to rear.......
Who fitted the PNM stuff......
What pads have you got......
Has the system been properly bled

The upgrade has been done many times and should give you a positive feel and outcome

[MPx]

No bite suggests to me not bled properly. Its a right PITA to do....and air can get trapped in the proportioning valves as well as the normal traps in the callipers.

My upgrade has always given good bite and stopping power, but I have experienced an alarming waywardness/squirming under proper heavy breaking. I think it was down to too much rearward bias when I put the twin pot Hispecs on the rear causing the rears to lock before the fronts. Because of the handbrake issue with that Hispec set up I had to swap to the PNM rear kit which I understand is a Golf derivative. Not had the issue since....but I suspect I could have got the same result from mucking about with the proportioning valves.

[Dom]

Morning. Thank you for your input.

The brakes were professionally fitted by Lakeside Engineering who have done this upgrade many times. The pads are Mintex 1144. The system has been re-bled by Lakeside after my initial concerns. The car behaved like this before the upgrade, so the issue has become two fold as I feel the brakes are not much better than the OE ones and the car is unstable during higher speed braking. I'll mention the proportioning valves to the garage as the car is currently with them having a PNM exhaust fitted, along with BCN's short shift kit.

Thanks again,

Dom

[rip]

Can you describe this in more detail?

Mine pulls a little & always has done but only when I slam on the brakes very hard. It is nothing more than a slight twitch which corrected itself so quickly that I felt back in control before it became a problem.
I have changed the front brakes, rear calipers (twice) all the brake lines & bled the system several times. None has made any difference.
It felt pressure related. Since upgrading my front brakes, I have so slam them on ridiculously hard to feel it, but it feel like the same foot pressure. Even emergency braking is not enough to cause this to happen.
I had my proportioning valves rebuilt this year due to seizure & have not noticed it since...but I have not braked heavily enough to expect it anyway.

[Fredjohn]

Having fitted Wilwood front and PNM rear brake upgrades, I can say that the braking is much improved and the car pulls up perfectly straight from 60/70mph under hard braking, although pedal feel is a bit soft. More bleeding required I think although I suspect one of the rear calipers has a small leak. To be investigated/winter project.

However, I did also strip down and clean the proportioning valves. They were filthy and full of gunge.

But back to basics: check your tyre pressures are all correct/even and that your tracking is spot on. Both of these will have an impact on stability, as will the road surface/camber/ruts. Make sure the road is smooth and flat and doesn't have HGV grooves running down it!

I have also had a full geometry set up done by Paul Matty: this has made a huge difference in the overall handling and inevitably will also help stability under braking. It had been so far out on 2 corners that they had to re-drill and weld 2 new mounting holes on the chassis and suspension arm: it had run off the scale of available shims from Lotus!

Keep the faith: pretty much everyone who has done these upgrades are pleased with the results.

[muley]

..TBH I never thought the HiSpec upgrade was much better than standard especially if the standard brakes were clean and free on the sliders with good pads. Might be better with the larger disk but I have no experience of that.



Jim

[Dom]

The tracking was done recently and the tyre pressures are correct. It only happens at speed and the braking doesn’t have to be overly heavy to cause it. The car feels floaty and lurches from side to side in wide arcs. The brakes themselves don’t inspire confidence as both bite and effect are not as positive as I’d like.

[rip]

..TBH I never thought the HiSpec upgrade was much better than standard especially if the standard brakes were clean and free on the sliders with good pads. Might be better with the larger disk but I have no experience of that.



Jim

I don't have HiSpecs. I have the Subaru disc/Vectra caliper combination.
Even with recently cleaned sliders, I thought he OEM calipers were poor compared to my daily.
The Subaru/Vectra combination is a world away from the OEM setup. Just ask ShaunM. He tried out mine when were at Snetterton a few years ago, braking from about 15-20 using the same pedal pressure he would in his Elan. I was glad to be wearing a seatbelt otherwise I would have found out if my head or the windscreen was tougher.
Mine don't warp the discs through overheating like the OEMs did either.

You are welcome to try mine out next time we meet.

[HJ2]

Ummmm... If this handling type was present before the upgrade, be it less. I would suspect tyres!
I upgraded to Wilwoods fronts and had the same experience. Then I went for Hi specs on the fronts, no improvements, still scary handling.
Then I replaced all tyres (Toyo R1R) and tadaaa! Perfect handling!

you could try to borrow wheels with good tyres to see if this cures your problem without spending a cent on brakes

[Dom]

Ummmm... If this handling type was present before the upgrade, be it less. I would suspect tyres!
I upgraded to Wilwoods fronts and had the same experience. Then I went for Hi specs on the fronts, no improvements, still scary handling.
Then I replaced all tyres (Toyo R1R) and tadaaa! Perfect handling!

you could try to borrow wheels with good tyres to see if this cures your problem without spending a cent on brakes

Interesting. But.... the tyres are new Toyos, albeit the Proxes.

[HJ2]

Ok, then you can skip that

[bbjon]

Your problem might be related to knackered shocks rather than a braking - if the shocks aren't able to control the springs under hard braking the car will feel squirrely.

[dapinky]

Just in case you haven't got enough variables to look at, I'd throw in a suggestion of raft bushes - if they are worn, they will throw the handling out under extremes of force direction change

[Dom]

I must admit shocks and bushes were at the top of my list. Of course, the front/rear proportioning valve needs looking at, too. Anyone got any reasonable front shocks knocking around?

[dapinky]

.... Anyone got any reasonable front shocks knocking around?

Unfortunate timing on your part - I posted my remaining hoarded OE suspension to another LEC member earlier today

[Dom]

.... Anyone got any reasonable front shocks knocking around?

Unfortunate timing on your part - I posted my remaining hoarded OE suspension to another LEC member earlier today

Doh!!!!

[Dom]

I’ve found the Fed shocks and springs at a good price. Would these be ok, as long as I fit both at the front at the same time?

[Rambo]

I think you'll find that the ride height is too high and the car will sit high

Someone correct me if I'm wrong. I usually am

[dapinky]

Mark, you are correct!

Although, some would argue that a 'new' shock will always be better than a worn one, even if 10mm higher (as long as both are the same).

I don't know if it is as simple as just the height, or if the valving is different as well (the FED has a different weight distribution to a UK car)???

Personally, I would prefer not to fit a FED unit, but if that is all you can lay your hands on, it's your shout.